Spark-plug.



B. A ,'EFFERY. I

SPARK PLUG.

APPLICATION FILED vac-9. 1913.

1,%3Z,@38D Patented July 3, 1917.

fijw, Z. 35 36' 11 w i2 56 WITNESSES PM W BENJAMIN A. JEFFERY, OF DETROIT, MICHIGAN.

SPARK-PLUG.

Specification of Letters Patent.

Patented July 3, 191?.

Application filed December 9, 1913. Serial No. 805,568.

To all whom it may concern Be it known that I, BENJAMIN A. JEF- FERY, a citizen of the United States, residing at Detroit, in the county of Wayne and State ofMichigan, have invented new and useful Imrovements-in Spark-Plugs, of which the following is a specification.

This invention relates to an improved spark plug.

One of the objects of the invention is to provide a spark plug providedwith an insulating block which carries the usual electrode, the latter having the same coeflicient of expansion as the insulating material surrounding the same. A further object is to provide an improved form of electrode. A

further object is to provide improved means for resisting the twisting or other strains incident to the operation of the usual bind.

ing nut which works on a threaded stud connected with .the electrode.

The invention will be hereinafter fully set forth and particularly pointed out in the claims.

In the accompanying drawings Figure 1 is a longitudinal sectional view of one form ofspark plug with my invention applied thereto. Fig. 2 is a similar view of a slight modification. Figs. 3 and 4 are opposite end views.

- Referring to the drawing, 10 designates a supporting shell provided with the usual screw threads 11 for engagement with the engine casing. Said shell is provided with a longitudinal bore which is offset to form an annular shoulder 12, the bore, above said shoulder, being internally threaded at 13. A bushing 14 engages said threads for the purpose of securing the insulating block in position.

The insulating block 16 is made of any suitable material, preferably porcelain, and is provided with an annular enlargement between its ends, said enlargement being in the form of a double cone formed by tapering the face of the block in opposite directions, as indicated at "17, 18, respectively. Surrounding the enlarged portion of, the insulating block 16 are packing collars 19, 2%, each collar being provided with a bore having the same degree of taper as the tapered portions 17, 18, each collar being provided with a flange 21. The adjacent flanges of the collars 19, 20, abut and are unite by a ferrule 22, the edges of which are bent oyer the respective flanges to prevent separation thereof. It will be noted that the bushing 15 is provided with a bore to receive the insulating block and collar 19, said bore being large enough to provide a slight radial clearance for the packing. The bore of the shell 10, adjacent shoulder 13, is also large enough to provide a slight radial clearance for the ferrule 22 and a similar clearance is provided for the packing ring 20.

In Fig. 2 I have illustrated a slight modification, which consists principally in dispensing with the bushing 15, and substituting therefor a ring or spacing piece 29 which rests upon the flange 21 of the collar 19. The ring 29, is forced longitudinally toward the shoulder 13, by crimping over the thin edge 30 on the upper portion of the shell, enough pressure being exerted to force the lower face of the flange 21 of collar 20 into a gas tight joint with the shoulder 13. The features thus far described form the subject matter of a separate application for patent and are not herein claimed.

The insulating block 16 is provided with a longitiudinal bore to receive a central stud 35, one end of which is threaded at 36 and projects beyond the end of the bore. The outer end of said bore is also enlarged to form a chamber for the reception of a shoul- .,der 37 formed on the stud 35, said stud being provided with a polygonal portion 38, preferably square, said polygonal portion being smaller than the shoulder 37 but extending from the latter. The end of the block 16 is also somewhat reduced, as indicated at 39, and provided with polygonal faces, preferably octagonal, to receive the flange 40 of a cap 41. Engaging the lower end of the stud 35 is a wire or electrode 42 provided with a special tip 42 formed of a suitable metal to withstand the heat of the gases and the action of the spark. The electrode 42 is formed of a metal having the same coefficient of expansion as the material of which the block 16 is formed, such a in the coolest portion of the plug. In the structures illustrated in the drawings, the stud is provided with a recess 43 in its lower end to receive the upper end of the wire 42, said recess being somewhat larger than the wire 42 to provide an intensifying gap. The shell 10 is provided with a grounded electrode 44 of any suitable or preferred construction.

In practice, the bore of the porcelain is partly filled with a suitable cement, some of which, when the shank of the stud is introduced into the bore, flows out and fills the space between the inside octagonal faces of the cap and the corresponding octagonal head of the porcelain. Before doing, this, however, the cap 41, which is provided with a square hole slightly smaller than the portion 38 is forced onto the latter, which is then upset, and its upper corners slightly swelled, which has the effect of riveting the cap to the stud.

The advantages of my improved spark,

plug will be readily apparent. It will be particularly noted that when a wire or terminal clip is placed between the cap 41 and the ordinary binding nut, and the latter tightened down, the tendency would be for the stud to pull up through the cap. This is resisted, however, by the shoulder 37. The only other strain of any consequence to which these parts might be subjected, is that which would be caused by a direct pull parallel with the axis of the plug. This the cement, which holds the shank of the stud 35 in the porcelain is easily able to care for. The use of the special alloy wire 42 between the stud 35 and the sparking point has proven very effective, in that the cement which holds it in place is not disintegrated as it is when a wire having an ordinary expansion coefiicient is used. This disintegra tion has the effect of permitting compression leakage and is caused b the relative movements efi'ect by the di erent expansions of the wire and porcelain. This trouble is overcome in my invention. Having thus explained the nature of my invention, and described an operative manner of constructing and using the same, although without attempting to set forth'all of the forms in which it may be made, or all of the modes of its use, what I claim is 1. An insulating block, an electrode extending into said block and having a protruding portion forming a binding post, a

ca secured to the protruding portion of said electrode .to prevent relative rotation, said block and cap being also provided with complemental angularly disposed faces to prevent relative rotation.

2. As an improvement in spark plugs, an insulating block, an electrode having a shank secured within said block, and a protruding portion forming a binding post, and a cap secured to the protruding portion, said cap and shank being provided with complemental angularly disposed faces to prevent relative rotation, said cap and block being also provided with complemental angularly disposed faces to prevent relative rotation.

3. As an improvement in spark plugs, an insulating block, an electrode having a shank secured within said block and provided with an angular portion, and a cap engaging said angular portion, the corners of the latter being upset over the top of said cap, said cap and insulating block being provided with complemental surfaces for preventing relative rotation.

4. As an improvement in spark plugs, an insulating block, a cap, an electrode having a shank secured within said block and a protruding portion forming a binding post, said shank being provided with an an nul-ar shoulder and a contiguous angular portion, the latter being upset over the top of said cap, said cap and insulating block being provided with complemental means for preventing relative rotation of the cap and block, the top of said cap resting upon said shoulder.

5.. As an improvement in spark plugs, an insulating block, an electrode member secured within said block and having a recess in one end, and an electrode wire formed of a material having the same coeflicient of eX- pansion as the material forming said block and smaller than the latter, said electrode being spaced from the wall of said recess t form an intensifying gap.

In testimony whereof I have hereunto set my hand in presence of two subscribing witnesses.

BENJAMIN A. J EFFERY. Witnesses:

JOSEPH A. JEFFERY, FRED. L. PARKER. 

